Speedo not working - please help

So I've had Trevor for 10 years, a 1999 4L Chimaera. The speedo was always a little difficult with the standard jump to 10 mph after moving for a while. The rev counter then started to become more problematic and started dancing whilst driving up and down. I tried to get someone to fix them but no one could take it on. I eventually ended up buying two new ones both from Caerbont.

I left them into my mechanic a year and a half ago to get them fitted. I'll not go into the story but boiled down the TVR is back with me and the speedo still doesn't work. He fitted both dials but couldn't get the speedo to work. Initially he said it was because of the Transducer so I ordered and got a Speedo Transducer - M0631 from TVRSSW and he fitted it. It still does not work, £1,000 later. TBH I feel a little like committing hari-kari in the garage but my wife wouldn't be impressed instead she wants me to get the car fixed so it can be sold. I can get the car MOT'd until the speedo is fixed.

So going up the road the speedo when the entire turns on goes from 0-180 and drops back to 0 (this would appear normal) when driving it says at 0 whilst building up speed and then jumps to 30. When driving at a constant 30 is jumps and drops between 30 and 20, occasionally dropping back to 0. This is more or less constant.

Is there anyone who has experience of this and can suggest a fix for this. I really am at my wits end and it would have been cheaper to drive the car to the mainland and get someone there to do it (we live in Northern Ireland) and the one guy who fixed TVRs here has retired, he was brilliant. If someone can come up with a solution I will try to fix a mechanic here who could implement it.

Really desperate, everything else with the car is 100% but this essentially prevents me driving Trevor and selling him.

All suggestions received.

Peter

So these are my dials. This is with the car off. Perhaps a stupid question but shouldn't the rev counter be a 0 when the car isnt even on?